Treatment method of silver-coated copper powder for low-temperature electronic paste

Abstract

The invention relates to the technical field of low-temperature electronic paste, in particular to a treatment method of silver-coated copper powder for low-temperature electronic paste. The treatment method comprises the following steps: (1) uniformly mixing silver-coated copper powder with a coating agent, filtering and drying to obtain a first treated object; (2) uniformly mixing the first treated substance with a coating agent, filtering, drying, cleaning with a cleaning agent, filtering again, and drying to obtain a second treated substance; (3) uniformly mixing the second treated substance with a coating agent, filtering, drying, cleaning with a cleaning agent, and drying to obtain a third treated substance; and (4) uniformly mixing the third treated object with a coating agent, filtering, drying, and then cleaning with a cleaning agent. According to the method, the silver-coated copper powder which is not completely coated can be further treated, and defects and test risks caused by incomplete coating are eliminated.

Description

Technical Field

[0001] The invention relates to the technical field of low-temperature electronic paste, and in particular to a method for processing silver-coated copper powder for low-temperature electronic paste. Background Art

[0002] Flexible printed circuits (FPCs) are highly favored for their excellent properties such as light weight, thin thickness, and free bending and folding. In the prior art, people in this field usually use low-temperature electronic paste to form a circuit pattern on an elastic substrate to obtain a flexible printed circuit board; the conductive filler in the low-temperature electronic paste used is usually a low-resistance metal powder, and the main component of the low-resistance metal powder is silver powder.

[0003] However, the cost of silver powder is relatively high, so generally, people in this field will use silver-coated copper powder to replace silver powder. However, silver-coated copper powder with low silver content (≤20%) has significant defects due to incomplete coating of part of the silver layer, resulting in the exposure of the internal copper layer: on the one hand, the appearance of the silver-coated copper powder will change from silver-gray to red-gray; on the other hand, in terms of performance, the exposed copper layer is not resistant to oxidation and water vapor, and after tests such as salt spray, high temperature, and hot and cold shock, the resistance will increase or be corroded due to oxidation of the copper layer or battery reaction.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a method for processing silver-coated copper powder (for low-temperature electronic paste), which can further process incompletely coated silver-coated copper powder to eliminate defects and testing risks caused by incomplete coating.

[0006] Specifically, the processing method includes:

[0007] Step (1), mixing the silver-coated copper powder and the coating agent uniformly, filtering and drying to obtain a first treated product;

[0008] Step (2), mixing the first treated product and the coating agent uniformly, filtering and drying, then washing with a cleaning agent, filtering again and drying to obtain a second treated product;

[0009] Step (3), mixing the second treated product and the coating agent uniformly, filtering and drying, and then washing with a cleaning agent, and drying to obtain a third treated product;

[0010] Step (4), mixing the third treated product and the coating agent uniformly, filtering and drying, and then washing with a cleaning agent.

[0011] The present invention unexpectedly discovered that the above treatment of incompletely coated silver-coated copper powder can effectively make up for the defect of exposed copper layer, thereby improving the overall performance of the silver-coated copper powder.

[0012] Those skilled in the art can set other parameters in the process according to common knowledge, which can all obtain effects equivalent to those described above in the present invention. However, there are also better technical solutions for other process parameters. For this reason, the present invention further explores and obtains the following preferred solutions.

[0013] Preferably, the coating agents in step (1) and step (3) are the same, both being the first coating agent; the first coating agent is selected from one or more of sodium silicate, sodium nitrite, ascorbic acid, siloxane, water, methanol, ethanol, acetone, trichloroacetic acid, and isopropylamine.

[0014] Preferably, the coating agents in step (2) and step (4) are the same, that is, the second coating agent; the second coating agent is selected from one or more of 2-mercaptobenzothiazole, benzotriazole, stearic acid, polyamide wax, diisopropyl ether, diisoamyl ether, isopentane, and ethyl acetate.

[0015] Preferably, in step (2), the cleaning agent is a first cleaning agent; the first cleaning agent is selected from one or more of quaternary ammonium salts, phosphate salts, sodium alkylbenzene sulfonate, polyacrylamide, water, glycerol, DMF, and acetic acid.

[0016] Preferably, in step (3), the cleaning agent is a second cleaning agent; the second cleaning agent is selected from one or more of oleic acid diethanolamide, diazolyl, propylene glycol, polyacrylate, dipropylene glycol methyl ether, and aromatic solvent oil.

[0017] Preferably, in step (4), the cleaning with a cleaning agent is divided into two steps: first, cleaning with a first cleaning agent for 1-3 times, and then cleaning with a second cleaning agent for 1-3 times; the first cleaning agent is selected from one or more of quaternary ammonium salts, phosphate salts, sodium alkylbenzene sulfonate, polyacrylamide, water, glycerol, DMF, and acetic acid, and the second cleaning agent is selected from one or more of oleic acid diethanolamide, diazolyl, propylene glycol, polyacrylate, dipropylene glycol methyl ether, and aromatic solvent oil.

[0018] According to the process system of the present invention, the coating agent and cleaning agent in each step are selected as above, which can further improve the coating rate and thus improve the quality of the silver-coated copper powder.

[0019] Preferably, the silver content of the silver-coated copper powder is ≤20%; the treatment method of the present invention is particularly suitable for silver-coated copper powder with a silver content of ≤20%; that is, the treatment effect is better when the silver-coated copper powder with a silver content of ≤20% is taken as the treatment object.

[0020] As a preferred technical solution, the processing method comprises the following steps:

[0021] (1) mixing the silver-coated copper powder and the first coating agent uniformly, filtering and drying to obtain a first treated product;

[0022] (2) mixing the first treated product and the second coating agent uniformly, filtering and drying, then washing with the first cleaning agent for 2-4 times, filtering again and drying to obtain the second treated product;

[0023] (3) mixing the second treated product and the first coating agent evenly, filtering and drying, and then washing with a second cleaning agent for 2-4 times, and drying to obtain a third treated product;

[0024] (4) mixing the third treated product and the second coating agent evenly, filtering and drying, and then washing with the first cleaning agent for 1 to 3 times, and then washing with the second cleaning agent for 1 to 3 times;

[0025] in,

[0026] The first coating agent is a mixture of sodium silicate, sodium nitrite, ascorbic acid, siloxane, water, trichloroacetic acid and isopropylamine in a weight ratio of 0.1-0.8: 0.4-0.6: 0.4-0.6: 0.2-0.9: 30-35: 30-35: 28-38;

[0027] The second coating agent is a mixture of 2-mercaptobenzothiazole, benzotriazole, stearic acid, polyamide wax, diisopropyl ether, diisoamyl ether, and isopentane in a weight ratio of 0.5-0.8: 0.5-0.6: 0.4-0.5: 0.2-0.5: 35-40: 35-40: 18-28;

[0028] The first cleaning agent is a mixture of quaternary ammonium salt, phosphate salt, sodium alkylbenzene sulfonate, polyacrylamide, water, DMF, and acetic acid in a weight ratio of 0.2-0.8: 0.5-0.6: 0.4-0.5: 0.2-0.8: 35-50: 30-35: 18-28;

[0029] The second cleaning agent is a mixture of oleic acid diethanolamide, diazolyl, propylene glycol, polyacrylate and dipropylene glycol methyl ether in a weight ratio of 0.5-1.5:0.5-1.5:35-40:35-40:18-28.

[0030] Based on the above scheme, the beneficial effects of the present invention are as follows:

[0031] The treatment method provided by the present invention is a brand-new technology for multi-layer protection of defective areas of silver-coated copper powder, and the method can effectively improve the anti-oxidation and anti-moisture capabilities of the silver-coated copper powder; the silver-coated copper powder treated by the method of the present invention will not have a significant increase in resistance or be non-conductive due to the anti-oxidation layer, and the anti-moisture protection layer will not be destroyed by the organic solvent in the low-temperature electronic slurry sample preparation process; and compared with other silver-coated copper powder repair processes, the treatment method of the present invention has a lower cost (without using complex equipment and high-priced raw materials). DETAILED DESCRIPTION

[0032] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0033] The silver-coated copper powder used in the embodiment is commercially available silver-coated copper powder with a silver content of 20%.

[0034] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0035] Example 1

[0036] This embodiment provides a method for processing silver-coated copper powder, comprising the following steps:

[0037] (1) mixing the silver-coated copper powder and the first coating agent uniformly, filtering and drying to obtain a first treated product;

[0038] (2) mixing the first treated product and the second coating agent uniformly, filtering and drying, then washing with the first cleaning agent for 4 times, filtering again and drying to obtain a second treated product;

[0039] (3) mixing the second treated product and the first coating agent evenly, filtering and drying, and then washing with the second cleaning agent for 4 times, and drying to obtain a third treated product;

[0040] (4) mixing the third treated product and the second coating agent evenly, filtering and drying, and then washing with the first cleaning agent for 3 times and then washing with the second cleaning agent for 3 times;

[0041] in,

[0042] The first coating agent is a mixture of sodium silicate, sodium nitrite, ascorbic acid, siloxane, water, trichloroacetic acid and isopropylamine in a weight ratio of 0.8:0.5:0.5:0.2:35:35:28;

[0043] The second coating agent is a mixture of 2-mercaptobenzothiazole, benzotriazole, stearic acid, polyamide wax, diisopropyl ether, diisoamyl ether, and isopentane in a weight ratio of 0.8:0.5:0.5:0.2:35:35:28;

[0044] The first cleaning agent is a mixture of quaternary ammonium salt, phosphate salt, sodium alkylbenzene sulfonate, polyacrylamide, water, DMF, and acetic acid in a weight ratio of 0.8:0.5:0.5:0.2:35:35:28;

[0045] The second cleaning agent is a mixture of oleic acid diethanolamide, diazolyl, propylene glycol, polyacrylate and dipropylene glycol methyl ether in a weight ratio of 1.5:0.5:35:35:28.

[0046] Example 2

[0047] This embodiment provides a method for processing silver-coated copper powder, comprising the following steps:

[0048] (1) mixing the silver-coated copper powder and the first coating agent uniformly, filtering and drying to obtain a first treated product;

[0049] (2) mixing the first treated product and the second coating agent uniformly, filtering and drying, then washing with the first cleaning agent for 3 times, filtering again and drying to obtain a second treated product;

[0050] (3) mixing the second treated product and the first coating agent evenly, filtering and drying, and then washing with the second cleaning agent for three times, and drying to obtain a third treated product;

[0051] (4) mixing the third treated product and the second coating agent evenly, filtering and drying, and then washing twice with the first cleaning agent and then washing twice with the second cleaning agent;

[0052] in,

[0053] The first coating agent is a mixture of sodium silicate, sodium nitrite, ascorbic acid, siloxane, water, trichloroacetic acid and isopropylamine in a weight ratio of 0.2:0.4:0.6:0.8:30:30:38;

[0054] The second coating agent is a mixture of 2-mercaptobenzothiazole, benzotriazole, stearic acid, polyamide wax, diisopropyl ether, diisoamyl ether, and isopentane in a weight ratio of 0.6:0.6:0.4:0.4:40:40:18;

[0055] The first cleaning agent is a mixture of quaternary ammonium salt, phosphate salt, sodium alkylbenzene sulfonate, polyacrylamide, water, DMF, and acetic acid in a weight ratio of 0.2:0.6:0.4:0.8:50:30:18;

[0056] The second cleaning agent is a mixture of oleic acid diethanolamide, diazolyl, propylene glycol, polyacrylate and dipropylene glycol methyl ether in a weight ratio of 0.5:1.5:40:40:18.

[0057] Example 3

[0058] This embodiment provides a method for processing silver-coated copper powder, comprising the following steps:

[0059] (1) mixing the silver-coated copper powder and the first coating agent uniformly, filtering and drying to obtain a first treated product;

[0060] (2) mixing the first treated product and the second coating agent uniformly, filtering and drying, then washing twice with the first cleaning agent, filtering again and drying to obtain a second treated product;

[0061] (3) mixing the second treated product and the first coating agent evenly, filtering and drying, and then washing twice with a second cleaning agent, and drying to obtain a third treated product;

[0062] (4) mixing the third treated product and the second coating agent evenly, filtering and drying, and then washing once with the first cleaning agent and then washing once with the second cleaning agent;

[0063] in,

[0064] The first coating agent is a mixture of sodium silicate, sodium nitrite, ascorbic acid, siloxane, water, trichloroacetic acid and isopropylamine in a weight ratio of 0.3:0.5:0.5:0.7:35:35:28;

[0065] The second coating agent is a mixture of 2-mercaptobenzothiazole, benzotriazole, stearic acid, polyamide wax, diisopropyl ether, diisoamyl ether, and isopentane in a weight ratio of 0.5:0.5:0.5:0.5:35:35:28;

[0066] The first cleaning agent is a mixture of quaternary ammonium salt, phosphate salt, sodium alkylbenzene sulfonate, polyacrylamide, water, DMF, and acetic acid in a weight ratio of 0.8:0.5:0.5:0.2:35:35:28;

[0067] The second cleaning agent is a mixture of oleic acid diethanolamide, diazolyl, propylene glycol, polyacrylate and dipropylene glycol methyl ether in a weight ratio of 1.5:0.5:35:35:28.

[0068] Example 4

[0069] This embodiment provides a method for processing silver-coated copper powder, comprising the following steps:

[0070] (1) mixing the silver-coated copper powder and the first coating agent uniformly, filtering and drying to obtain a first treated product;

[0071] (2) mixing the first treated product and the second coating agent uniformly, filtering and drying, then washing with the first cleaning agent for 3 times, filtering again and drying to obtain a second treated product;

[0072] (3) mixing the second treated product and the first coating agent evenly, filtering and drying, and then washing with the second cleaning agent for 4 times, and drying to obtain a third treated product;

[0073] (4) mixing the third treated product and the second coating agent evenly, filtering and drying, and then washing once with the first cleaning agent and then washing twice with the second cleaning agent;

[0074] in,

[0075] The first coating agent is a mixture of sodium silicate, sodium nitrite, ascorbic acid, siloxane, water, trichloroacetic acid and isopropylamine in a weight ratio of 0.1:0.6:0.4:0.9:35:33:30;

[0076] The second coating agent is a mixture of 2-mercaptobenzothiazole, benzotriazole, stearic acid, polyamide wax, diisopropyl ether, diisoamyl ether, and isopentane in a weight ratio of 0.8:0.5:0.5:0.2:35:35:28;

[0077] The first cleaning agent is a mixture of quaternary ammonium salt, phosphate salt, sodium alkylbenzene sulfonate, polyacrylamide, water, DMF, and acetic acid in a weight ratio of 0.8:0.5:0.5:0.2:35:35:28;

[0078] The second cleaning agent is a mixture of oleic acid diethanolamide, diazolyl, propylene glycol, polyacrylate and dipropylene glycol methyl ether in a weight ratio of 1.5:0.5:35:35:28.

[0079] Comparative Example 1

[0080] This comparative example provides a method for treating silver-coated copper powder, which differs from Example 1 in that steps (2) to (4) are not performed.

[0081] Comparative Example 2

[0082] This comparative example provides a method for treating silver-coated copper powder, which differs from Example 1 in that steps (3) to (4) are not performed.

[0083] Comparative Example 3

[0084] This comparative example provides a method for treating silver-coated copper powder, which differs from Example 1 in that the treatment in step (4) is not performed.

[0085] Test example

[0086] This test example performs performance tests on untreated silver-coated copper powder and silver-coated copper powder treated by Examples 1-4 and Comparative Examples 1-3, as follows:

[0087] 1. Silver-coated copper powder resistivity test: Use powder resistivity tester for testing;

[0088] 2. Appearance of silver-coated copper powder: visual observation;

[0089] 3. Circuit square resistance test: Make each silver-coated copper powder into low-temperature electronic paste, and then use the low-temperature electronic paste to form a conductive circuit on the substrate by screen printing. After curing, test the square resistance of each conductive circuit;

[0090] 4. Circuit salt spray test: Make each silver-coated copper powder into low-temperature electronic paste, and then use the low-temperature electronic paste to form a conductive circuit on the substrate by screen printing. After curing, perform salt spray test on each conductive circuit and observe the appearance; the test temperature is 35±2℃, the solution concentration is 5±0.1%, the pH is between 6.5-7.2, and the test time is 8h;

[0091] 5. Circuit hot and cold shock test: Make each silver-coated copper powder into low-temperature electronic paste, and then use the low-temperature electronic paste to form a conductive circuit on the substrate by screen printing. After curing, perform hot and cold shock tests on each conductive circuit, observe the appearance, and test the resistance change rate ΔR; the test conditions are 55±2℃95%RH, the test time is 120h, and the recovery time is 2h;

[0092] 6. Circuit high temperature storage test: Store each silver-coated copper powder at 60°C for 240 hours and test the resistance change rate ΔR;

[0093] 7. The test results are shown in Table 1;

[0094] Table 1

[0095]

[0096]

[0097] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for processing silver-coated copper powder, characterized in that: include: Step (1), mixing the silver-coated copper powder and the coating agent uniformly, filtering and drying to obtain a first treated product; Step (2), mixing the first treated product and the coating agent uniformly, filtering and drying, then washing with a cleaning agent, filtering again and drying to obtain a second treated product; Step (3), mixing the second treated product and the coating agent uniformly, filtering and drying, and then washing with a cleaning agent, and drying to obtain a third treated product; Step (4), mixing the third treated product and the coating agent uniformly, filtering and drying, and then washing with a cleaning agent.

2. The processing method according to claim 1, characterized in that: The coating agents in step (1) and step (3) are the same, both of which are the first coating agent; the first coating agent is selected from one or more of sodium silicate, sodium nitrite, ascorbic acid, siloxane, water, methanol, ethanol, acetone, trichloroacetic acid, and isopropylamine.

3. The processing method according to claim 1 or 2, characterized in that: The coating agent in step (2) is the same as that in step (4), which is a second coating agent; the second coating agent is selected from one or more of 2-mercaptobenzothiazole, benzotriazole, stearic acid, polyamide wax, diisopropyl ether, diisoamyl ether, isopentane, and ethyl acetate.

4. The processing method according to any one of claims 1 to 3, characterized in that: In step (2), the cleaning agent is a first cleaning agent; the first cleaning agent is selected from one or more of quaternary ammonium salts, phosphate salts, sodium alkylbenzene sulfonate, polyacrylamide, water, glycerol, DMF, and acetic acid.

5. The processing method according to any one of claims 1 to 4, characterized in that: In step (3), the cleaning agent is a second cleaning agent; the second cleaning agent is selected from one or more of oleic acid diethanolamide, diazolyl, propylene glycol, polyacrylate, dipropylene glycol methyl ether, and aromatic solvent oil.

6. The processing method according to any one of claims 1 to 5, characterized in that: In step (4), the cleaning with a cleaning agent is divided into two steps: first, cleaning with a first cleaning agent for 1-3 times, and then cleaning with a second cleaning agent for 1-3 times; the first cleaning agent is selected from one or more of quaternary ammonium salts, phosphate salts, sodium alkylbenzene sulfonate, polyacrylamide, water, glycerol, DMF, and acetic acid, and the second cleaning agent is selected from one or more of oleic acid diethanolamide, diazolidine, propylene glycol, polyacrylate, dipropylene glycol methyl ether, and aromatic solvent oil.

7. The processing method according to claim 1, characterized in that: The silver content of the silver-coated copper powder is ≤20%.

8. The processing method according to claim 1, characterized in that: The steps include: (1) mixing the silver-coated copper powder and the first coating agent uniformly, filtering and drying to obtain a first treated product; (2) mixing the first treated product and the second coating agent uniformly, filtering and drying, then washing with the first cleaning agent for 2-4 times, filtering again and drying to obtain the second treated product; (3) mixing the second treated product and the first coating agent evenly, filtering and drying, and then washing with a second cleaning agent for 2-4 times, and drying to obtain a third treated product; (4) mixing the third treated product and the second coating agent evenly, filtering and drying, and then washing with the first cleaning agent for 1 to 3 times, and then washing with the second cleaning agent for 1 to 3 times; in, The first coating agent is a mixture of sodium silicate, sodium nitrite, ascorbic acid, siloxane, water, trichloroacetic acid and isopropylamine in a weight ratio of 0.1-0.8: 0.4-0.6: 0.4-0.6: 0.2-0.9: 30-35: 30-35: 28-38; The second coating agent is a mixture of 2-mercaptobenzothiazole, benzotriazole, stearic acid, polyamide wax, diisopropyl ether, diisoamyl ether, and isopentane in a weight ratio of 0.5-0.8: 0.5-0.6: 0.4-0.5: 0.2-0.5: 35-40: 35-40: 18-28; The first cleaning agent is a mixture of quaternary ammonium salt, phosphate salt, sodium alkylbenzene sulfonate, polyacrylamide, water, DMF, and acetic acid in a weight ratio of 0.2-0.8: 0.5-0.6: 0.4-0.5: 0.2-0.8: 35-50: 30-35: 18-28; The second cleaning agent is a mixture of oleic acid diethanolamide, diazolyl, propylene glycol, polyacrylate and dipropylene glycol methyl ether in a weight ratio of 0.5-1.5:0.5-1.5:35-40:35-40:18-28.

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